Project Summary: Genetic Modification of Health-promoting Isoflavones

Biosynthesis and genetic modification of isoflavonoids

Project objectives:
Isoflavonoids are a class of plant natural products found primarily in legumes. Our interest in isoflavonoids stems from the effect these compounds have on plant and animal health. Several isoflavonoids have antimicrobial activity and may play a role in plant defense. One example is the phytoalexin medicarpin from alfalfa whose synthesis is induced in response to pathogen attack. The biochemical pathway leading to the biosynthesis of medicarpin in alfalfa is well characterized and therefore amenable to genetic manipulation to enhance defense responses.

The effect of isoflavonoids on animals was first documented in the 1940’s when it was noted that sheep grazed on subterranean clover had problems with reproduction and fertility. It is now known that certain isoflavonoids have estrogenic activity (termed “phytoestrogens”) and can have a direct impact on animal health. Soybean contains large amounts of the isoflavone phytoestrogens genistein and daidzein and soy products are the main dietary source of isoflavones for humans. There is an extensive literature suggesting that dietary intake of isoflavones may have beneficial effects on diseases such as cancer and heart disease as well as the symptoms of menopause. However, not all of the literature on the health benefits of isoflavones is positive and more research into this area is warranted before isoflavones can be truly considered “nutriceuticals”.

Current projects in the lab include engineering isoflavonoid phytoestrogens in plants to define factors impacting isoflavonoid production in legumes and non-legumes. We are also generating plants with defined levels of isoflavonoid phytoestrogens for detailed animal feeding studies designed to assess the health benefits of plant-derived isoflavones.

We are also continuing to identify and characterize enzymes of isoflavonoid biosynthesis and their potential interactions with one another. We are particularly interested in enzymes that modify isoflavones (via prenylation, glycosylation, methylation, etc) with the potential to alter their biological activity. We are testing a high-throughput functional genomics approach to identify isoflavonoid glycosyl transferases from Medicago truncatula.

Present Lab Personnel on Project:

Collaborators

Dr. Xiaoqiang Wang, Noble Foundation
Dr Daneel Ferreira, University of Mississippi, Oxford, MS
Dr Joe Noel, Salk Institute
Dr Lloyd Sumner, Noble Foundation
Dr Lance Whaley, Texas A and M University, Commerce, TX

Past Personnel

Dr. Li Tian
Dr. Bettina Deavours
Dr. Chang-Jun Liu
Dr. Chris Steele

Funding Sources

Oklahoma Center for the Advancement of Science and Technology Health Sciences Program
Noble Foundation

Recent Publications:

Modolo, L.V., Pang, Y., Tian, L. and Dixon, R.A. (2008). Gene discovery and metabolic engineering in the phenylpropanoid pathway. Recent Advances in Polyphenols Research, 1, in press.
Farag, M.A., Huhman, D.V., Dixon, R.A. and Sumner, L.W. (2008).Metabolomics reveals novel pathways and differential mechanistic and elicitor-specific responses in phenylpropanoid and isoflavonoid biosynthesis in Medicago truncatula cell cultures. Plant Physiology 146, 387-402.
Farag, M.A., Deavours, B.E., De-Fatima, A., Naoumkina, M., Dixon, R.A. and Sumner, L.W. (2008) Integrated metabolite and transcript profiling identifies peroxidases involved in aurone biosynthesis in Medicago truncatula cell cultures. Plant Cell, in review.
He, X.-Z., Li, W.-S., Blount, J.W. and Dixon, R.A. (2008). Regioselective synthesis of plant flavonoid glycosides in E.coli. Applied Microbiology and Biotechnology 80, 253-260.
Naoumkina, M. and Dixon, R.A. (2008) Subcellular localization of flavonoid natural products- a signaling function? Plant Signaling and Behavior, in press.
Naoumkina, M., He, X-Z. and Dixon, R.A. (2008). Elicitor-induced transcription factors for metabolic reprogramming of secondary metabolism in Medicago truncatula. BMC Plant Biology 8, 132.
Modolo, L., Blount, J.W., Achnine, L., Naoumkina, M., Wang, X. and Dixon, R.A. (2007) A functional genomics approach to (iso)flavonoid glycosylation in the model legume Medicago truncatula. Plant Molecular Biology 64, 499-518.
Shao, H., Dixon, R.A. and Wang, X. (2007) Crystal structure of vestitone reductase from alfalfa (Medicago sativa L.). Journal of Molecular Biology 369, 265-276.
Li, L., Modolo, L.V., Escamilla-Trevino, L.L., Achnine, L., Dixon, R.A. and Wang, X. (2007) Crystal structure of Medicago truncatula UGT85H2 - insights into the structural basis of a multifunctional (iso)flavonoid glycosyltransferase. Journal of Molecular Biology 370, 951-963.
Naoumkina, M., Farag, M.A., Sumner, L.W., Tang, Y., Liu, C.-J. and Dixon, R.A. (2007) Different mechanisms for phytoalexin induction by pathogen- and wound signals in Medicago truncatula. Proceedings of the National Academy of Sciences USA 104, 17909-17915.
Tian, L., Pang, Y. and Dixon, R.A. (2007). Biosynthesis and genetic engineering of proanthocyanidins and (iso)flavonoids. Phytochemistry Reviews, in press.
Marais, J.P.J., Deavours, B.E., Dixon, R.A. and Ferreira, D. (2006). The stereochemistry of flavonoids. In The Science of Flavonoids, ed E. Grotewold, Springer, pp1-46.
Liu, C.-J., Deavours, B.E., Richard, S.B., Ferrer, J.-L., Blount, J.W., Huhman, D., Dixon, R.A. and Noel, J.P. (2006). Structural basis for dual functionality of isoflavonoid O-methyltransferases in the evolution of plant defense responses. Plant Cell 18, 3656-3669.
Tian, L., Blount, J.W. and Dixon, R.A. (2006). Phenylpropanoid glycosyltransferases from osage orange (Maclura pomifera) fruit. FEBS Letters, 580, 6915-6920
Tian, L. and Dixon, R.A. (2006). An artificial bifunctional enzyme for engineering of isoflavone metabolism in non-legume plants. Planta, 224, 496-507.
Wang, X., He, X., Lin, J., Shao, H., Chang, Z.Z. and Dixon, R.A. (2006) Crystal structure of isoflavone reductase from alfalfa (Medicago sativa L.). Journal of Molecular Biology 358, 1341-1352.
Deavours, B.E., Liu, C.-J., Naoumkina, M.A., Tang, Y., Farag, M.A., Sumner, L.W., Noel, J.P. and Dixon, R.A. (2006). Functional analysis of members of the isoflavone and isoflavanone O-methyltransferase enzyme families from the model legume Medicago truncatula. Plant Molecular Biology 62,715-733.
Liu, C.-J., Deavours, B.E., Richard, S.B., Ferrer, J.-L., Blount, J.W., Huhman, D., Dixon, R.A. and Noel, J.P. (2006). Structural basis for dual functionality of isoflavonoid O-methyltransferases in the evolution of plant defense responses. Plant Cell 18, 3656-3669.
Deavours, B.E. and Dixon, R.A. (2005). Metabolic engineering of isoflavonoid biosynthesis in alfalfa (Medicago sativa L.). Plant Physiology 138, 2245-2259.
Dixon, R.A. (2004) Phytoestrogens. Annual Review of Plant Biology 55, 225-261.
Liu, C-J., Huhman, D., Sumner, L.W. and Dixon, R.A. (2003) Regiospecific hydroxylation of isoflavones by cytochrome P450 81E enzymes from Medicago truncatula. Plant Journal 36: 471-484.
Liu, C-J., Blount, J.W., Steele, C.L. and Dixon, R.A. (2002). Bottlenecks for the metabolic engineering of isoflavone glycoconjugates in Arabidopsis. Proceedings of the National Academy of Sciences USA 99, 14578-14583.
Liu, C-J. and Dixon, R.A. (2001). Elicitor-induced association of isoflavone O-methyltransferase with endomembranes prevents formation and 7-O-methylation of daidzein during isoflavonoid phytoalexin biosynthesis. Plant Cell 13: 2643-2658.
Zubieta, C., Dixon, R.A. and Noel, J. (2001). Crystal structures of chalcone O-methyltransferase and isoflavone O-methyltransferase reveal the structural basis for substrate specificity in plant O-methyltransferases. Nature Structural Biology 8: 271-279.
He, X.-Z. and Dixon, R.A. (2000). Genetic manipulation of isoflavone 7-O-methyltransferase enhances the biosynthesis of 4’-O-methylated isoflavonoid phytoalexins and disease resistance in alfalfa. Plant Cell 12: 1689-1702